Note: Ok for this question, I used cos A= sqrt(1-sin A^2) and got sqrt((10-sqrt10)/10).   <----- Mistake


cos A=  =  =  =  =  =      


Notice that the sign of square root was chosen "+" since the angle A is in Q1.

My question is: Why do you need cos A?.

To find tan (A + B) and cot (A + B), you only need: tan A and tan B, since , and 



, so y = , while r = 10

To find x, we get:  ------>  ------> , or , or 

Now you have: , or 



, so now you have all you need to find what you're looking for. 

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